/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.tsfile.write.page;

import org.apache.iotdb.tsfile.compress.ICompressor;
import org.apache.iotdb.tsfile.encoding.encoder.Encoder;
import org.apache.iotdb.tsfile.file.metadata.enums.CompressionType;
import org.apache.iotdb.tsfile.file.metadata.statistics.TimeStatistics;
import org.apache.iotdb.tsfile.utils.PublicBAOS;
import org.apache.iotdb.tsfile.utils.ReadWriteForEncodingUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.WritableByteChannel;

/**
 * This writer is used to write time into a page. It consists of a time encoder and respective
 * OutputStream.
 */
public class TimePageWriter {

    private static final Logger logger = LoggerFactory.getLogger(TimePageWriter.class);

    private final ICompressor compressor;

    // time
    private Encoder timeEncoder;
    private final PublicBAOS timeOut;

    /**
     * statistic of current page. It will be reset after calling {@code
     * writePageHeaderAndDataIntoBuff()}
     */
    private TimeStatistics statistics;

    public TimePageWriter(Encoder timeEncoder, ICompressor compressor) {
        this.timeOut = new PublicBAOS();
        this.timeEncoder = timeEncoder;
        this.statistics = new TimeStatistics();
        this.compressor = compressor;
    }

    /**
     * write a time into encoder
     */
    public void write(long time) {
        timeEncoder.encode(time, timeOut);
        statistics.update(time);
    }

    /**
     * write time series into encoder
     */
    public void write(long[] timestamps, int batchSize, int arrayOffset) {
        for (int i = arrayOffset; i < batchSize + arrayOffset; i++) {
            timeEncoder.encode(timestamps[i], timeOut);
        }
        statistics.update(timestamps, batchSize, arrayOffset);
    }

    /**
     * flush all data remained in encoders.
     */
    private void prepareEndWriteOnePage() throws IOException {
        timeEncoder.flush(timeOut);
    }

    /**
     * getUncompressedBytes return data what it has been written in form of <code>
     * size of time list, time list, value list</code>
     *
     * @return a new readable ByteBuffer whose position is 0.
     */
    public ByteBuffer getUncompressedBytes() throws IOException {
        prepareEndWriteOnePage();
        ByteBuffer buffer = ByteBuffer.allocate(timeOut.size());
        buffer.put(timeOut.getBuf(), 0, timeOut.size());
        buffer.flip();
        return buffer;
    }

    /**
     * write the page header and data into the PageWriter's output stream.
     */
    public int writePageHeaderAndDataIntoBuff(PublicBAOS pageBuffer, boolean first)
            throws IOException {
        if (statistics.getCount() == 0) {
            return 0;
        }

        ByteBuffer pageData = getUncompressedBytes();
        int uncompressedSize = pageData.remaining();
        int compressedSize;
        byte[] compressedBytes = null;

        if (compressor.getType().equals(CompressionType.UNCOMPRESSED)) {
            compressedSize = uncompressedSize;
        } else if (compressor.getType().equals(CompressionType.GZIP)) {
            compressedBytes =
                    compressor.compress(pageData.array(), pageData.position(), uncompressedSize);
            compressedSize = compressedBytes.length;
        } else {
            compressedBytes = new byte[compressor.getMaxBytesForCompression(uncompressedSize)];
            // data is never a directByteBuffer now, so we can use data.array()
            compressedSize =
                    compressor.compress(
                            pageData.array(), pageData.position(), uncompressedSize, compressedBytes);
        }

        // write the page header to IOWriter
        int sizeWithoutStatistic = 0;
        if (first) {
            sizeWithoutStatistic +=
                    ReadWriteForEncodingUtils.writeUnsignedVarInt(uncompressedSize, pageBuffer);
            sizeWithoutStatistic +=
                    ReadWriteForEncodingUtils.writeUnsignedVarInt(compressedSize, pageBuffer);
        } else {
            ReadWriteForEncodingUtils.writeUnsignedVarInt(uncompressedSize, pageBuffer);
            ReadWriteForEncodingUtils.writeUnsignedVarInt(compressedSize, pageBuffer);
            statistics.serialize(pageBuffer);
        }

        // write page content to temp PBAOS
        logger.trace(
                "start to flush a time page data into buffer, buffer position {} ", pageBuffer.size());
        if (compressor.getType().equals(CompressionType.UNCOMPRESSED)) {
            try (WritableByteChannel channel = Channels.newChannel(pageBuffer)) {
                channel.write(pageData);
            }
        } else {
            pageBuffer.write(compressedBytes, 0, compressedSize);
        }
        logger.trace(
                "finish flushing a time page data into buffer, buffer position {} ", pageBuffer.size());
        return sizeWithoutStatistic;
    }

    /**
     * calculate max possible memory size it occupies, including time outputStream and value
     * outputStream, because size outputStream is never used until flushing.
     *
     * @return allocated size in time, value and outputStream
     */
    public long estimateMaxMemSize() {
        return timeOut.size() + timeEncoder.getMaxByteSize();
    }

    /**
     * reset this page
     */
    public void reset() {
        timeOut.reset();
        statistics = new TimeStatistics();
    }

    public void setTimeEncoder(Encoder encoder) {
        this.timeEncoder = encoder;
    }

    public void initStatistics() {
        statistics = new TimeStatistics();
    }

    public long getPointNumber() {
        return statistics.getCount();
    }

    public TimeStatistics getStatistics() {
        return statistics;
    }
}
